ASP. NET 2.0 XML series (4): xmlreader class Introduction

 

(This article is from msdn)

Xmlreader is an abstract base class that provides non-Cache and read-only access to XML data. This class complies with the W3C Extensible Markup Language (XML) 1.0 and XML namespace recommendations.

Xmlreader supports reading XML data from streams or files. The methods and attributes defined by this class allow you to browse data and read the content of the node. The current node refers to the node where the reader is located. Use any read methods and attributes that return the current node value to promote the reader.

Xmlreader class allows you:

• Check whether the characters are valid xml characters, and whether the element and attribute names are valid XML names.

• Check whether the XML document format is correct.

• Validate data according to the DTD or architecture.

• Retrieve data from an XML Stream or skip unnecessary records using the extraction model.

Before using xmlreader to read XML documents, we need to know the attributes and methods of this class and the types of the node xmlnode.

1. attributes of the xmlreader class

Name	Description
Attributecount	When a derived class is overwritten, the number of attributes on the current node is obtained.
Baseuri	When a derived class is overwritten, the base URI of the current node is obtained.
Canreadbinarycontent	Gets a value indicating whether xmlreader can read binary data.
Canreadvaluechunk	Gets a value that indicatesXmlreaderWhether to implement the readvaluechunk method.
Canresolveentity	Gets a value that indicates whether the reader can analyze and parse entities.
Depth	When a derived class is overwritten, the depth of the current node in the XML document is obtained.
EOF	Gets a value that indicates whether the reader is positioned at the end of the stream when it is overwritten in a derived class.
Hasattributes	Gets a value indicating whether the current node has any attributes.
Hasvalue	When a derived class is overwritten, a value is obtained, which indicates whether the current node can have a value.
Isdefault	When a derived class is overwritten, a value is obtained to indicate whether the current node is an attribute generated from the default value defined in The DTD or architecture.
Isemptyelement	Gets a value that indicates whether the current node is a null element (for example<Myelement/>).
Item	Overloaded. Obtain the value of this attribute when it is overwritten in a derived class.
Localname	When a derived class is overwritten, obtain the local name of the current node.
Name	When it is overwritten in a derived class, get the qualified name of the current node.
Namespaceuri	When a derived class is overwritten, retrieve the namespace URI of the node on which the reader locates (in the form defined in W3C namespace specifications ).
Nametable	When a derived class is overwritten, The xmlnametable associated with the implementation is obtained.
Nodetype	When a derived class is overwritten, the type of the current node is obtained.
Prefix	When a derived class is overwritten, The namespace prefix associated with the current node is obtained.
Quotechar	When a derived class is overwritten, the quotation mark character used to enclose the attribute node value is obtained.
Readstate	Gets the reader status when it is overwritten in a derived class.
Schemainfo	Obtain the schema information allocated to the current node as the schema verification result.
Settings	ObtainXmlreaderThe xmlreadersettings object of the instance.
Value	When a derived class is overwritten, the text value of the current node is obtained.
Valuetype	Obtain the Common Language Runtime Library (CLR) Type of the current node.
Xmllang	Obtain the currentXML: LangRange.
Xmlspace	Obtain the currentXML: SpaceRange.

 

2. xmlreader Class Method

 

Name	Description
Close	When it is overwritten in a derived class, change readstateClosed.
Create	Overloaded. Create a new xmlreader instance.
Equals	Overloaded. Determine whether the two object instances are equal. (Inherit from object .)
Getattribute	Overloaded. When a derived class is overwritten, the attribute value is obtained.
Gethashcode	Used as a hash function of a specific type. Gethashcode is suitableAlgorithmAnd data structures (such as hash tables. (Inherit from object .)
GetType	Obtain the type of the current instance. (Inherit from object .)
Isname	Gets a value that indicates whether the string parameter is a valid XML name.
Isnametoken	Gets a value that indicates whether the string parameter is a valid XML name tag.
Isstartelement	Overloaded. Test whether the current content node is a start tag.
Lookupnamespace	When it is overwritten in a derived class, the namespace prefix is resolved within the range of the current element.
Movetoattribute	Overloaded. When it is overwritten in a derived class, it is moved to the specified attribute.
Movetocontent	Check whether the current node is content (non-blank text,CDATA,Element,Endelement,EntityreferenceOrEndentity. If this node is not a content node, the reader jumps forward to the next content node or the end of the file. It skips the following types of nodes:Processinginstruction,Documenttype,Comment,WhitespaceOrSignificantwhitespace.
Movetoelement	When it is overwritten in a derived class, it is moved to an element that contains the current attribute node.
Movetofirstattribute	When it is overwritten in a derived class, it is moved to the first attribute.
Movetonextattribute	When it is overwritten in a derived class, it is moved to the next attribute.
Read	When a derived class is overwritten, the next node is read from the stream.
Readattributevalue	When a derived class is overwritten, the attribute value is parsed into one or moreText,EntityreferenceOrEndentityNode.
Readcontentas	Read the content as an object of the specified type.
Readcontentasbase64	Read the content and return the base64 decoded binary bytes.
Readcontentasbinhex	Read content and returnBinhexThe decoded binary bytes.
Readcontentasboolean	Use the text content of the current locationBooleanRead.
Readcontentasdatetime	Reads the text content of the current position as a datetime object.
Readcontentasdecimal	Read the text content of the current location as a decimal object.
Readcontentasdouble	Read the text content at the current position as a double-precision floating point number.
Readcontentasfloat	Read the text content at the current position as a single-precision floating point number.
Readcontentasint	Read the text content of the current position as a 32-bit signed integer.
Readcontentaslong	Read the text content of the current position as a 64-bit signed integer.
Readcontentasobject	Use the text content of the current locationObjectRead.
Readcontentasstring	Read the text content of the current position as a string object.
Readelementcontentas	Overloaded. Read the current element and return the content as an object of the specified type.
Readelementcontentasbase64	Read the element andBase64Decode the content.
Readelementcontentasbinhex	Read the element andBinhexDecode the content.
Readelementcontentasboolean	Overloaded. Read the current element value as a Boolean object.
Readelementcontentasdatetime	Overloaded. Read the current element and use the contentDatetimeObject.
Readelementcontentasdecimal	Overloaded. Use the current element valueDecimalObject reading.
Readelementcontentasdouble	Overloaded. Read the current element and return the content as a double-precision floating point number.
Readelementcontentasfloat	Overloaded. Read the current element value as a single-precision floating point number.
Readelementcontentasint	Overloaded. Read the current element and return the content as a 32-bit signed integer.
Readelementcontentaslong	Overloaded. Read the current element and return the content as a 64-bit signed integer.
Readelementcontentasobject	Overloaded. Read the current element and use the contentObject.
Readelementcontentasstring	Overloaded. Read the current element and use the contentStringObject.
Readelementstring	Overloaded. This is a helper Method for reading simple plain text elements.
Readendelement	Check whether the current content node is the end mark and push the reader to the next node.
Readinnerxml	When a derived class is overwritten, all content (including tags) is read as strings.
Readouterxml	When a derived class is overwritten, read indicates the node and all its sub-level content (including tags ).
Readstartelement	Overloaded. Check whether the current node is an element and push the reader to the next node.
Readstring	When a derived class is overwritten, the content of the element or text node is read as a string.
Readsubtree	Returns the newXmlreaderInstance, which can be used to read the current node and all its subnodes.
Readtodescendant	Overloaded. LetXmlreaderForward to the next matched child element.
Readtofollowing	Overloaded. Read until the named element is found.
Readtonextsibling	Overloaded. LetXmlreaderForward to the next matched peer element.
Readvaluechunk	Read a large number of text streams embedded in XML documents.
Referenceequals	Determine the specifiedObjectWhether the instance is the same. (Inherit from object .)
Resolveentity	When it is overwritten in a derived classEntityreferenceObject reference of a node.
Skip	Skip the sublevel of the current node.
Tostring	Returns the currentObjectOfString. (Inherit from object .)

 

3. xmlnodetype enumeration member

 

Member name	Description
Attribute	Properties (for example,Id = '000000').AttributeA node can have the following subnode types:TextAndEntityreference.AttributeA node does not appear as a subnode of any other node type. Do not treat itElement.
CDATA	CDATA section (for example,<! [CDATA [My escaped text]>). The CDATA section is used to escape text blocks that will be recognized as tags.CDATAA node cannot have any subnodes. It can useDocumentfragment,EntityreferenceAndElementNode sublevel.
Comment	Annotations (for example,<! -- My comment -->).CommentA node cannot have any subnodes. It can useDocument,Documentfragment,ElementAndEntityreferenceNode sublevel.
Document	The document object that serves as the root of the document tree provides access to the entire XML document.DocumentA node can have the following subnode types:Xmldeclaration,Element(Up to one ),Processinginstruction,CommentAndDocumenttype. It cannot appear in any node type sublevel.
Documentfragment	Document snippets.DocumentfragmentA node associates a node or subtree with a document and is not actually included in this document.DocumentfragmentA node can have the following subnode types:Element,Processinginstruction,Comment,Text,CDATAAndEntityreference. It cannot appear in any node type sublevel.
Documenttype	The document type declaration indicated by the following mark (for example,<! Doctype...>).DocumenttypeA node can have the following subnode types:NotationAndEntity. It can useDocumentNode sublevel.
Element	Element (for example,<Item>).ElementA node can have the following subnode types:Element,Text,Comment,Processinginstruction,CDATAAndEntityreference. It can beDocument,Documentfragment,EntityreferenceAndElementThe child level of the node.
Endelement	End Element tag (for example,</Item>). When xmlreader reaches the end of an elementEndelementNode.
Endentity	Because resolveentity is calledXmlreaderReturn when the end of object replacement is reached.
Entity	Entity declaration (for example,<! Entity...>).EntityNodes can have child nodes that indicate expanded entities (for exampleTextAndEntityreferenceNode ). It can useDocumenttypeNode sublevel.
Entityreference	Entity reference (for example,& Num;).EntityreferenceA node can have the following subnode types:Element,Processinginstruction,Comment,Text,CDATAAndEntityreference. It can useAttribute,Documentfragment,ElementAndEntityreferenceNode sublevel.
None	If notReadMethodXmlreader.
Notation	Representation in document type declaration (for example,<! Notation...>).NotationA node cannot have any subnode. It can useDocumenttypeNode sublevel.
Processinginstruction	Processing commands (for example,<? Pi test?>).ProcessinginstructionA node cannot have any subnode. It can useDocument,Documentfragment,ElementAndEntityreferenceNode sublevel.
Significantwhitespace	Blank orXML: Space = "preserve"Blank in the range.
Text	The text content of the node.TextA node cannot have any subnode. It can useAttribute,Documentfragment,ElementAndEntityreferenceThe child node of the node.
Whitespace	Blank between tags.
Xmldeclaration	XML declaration (for example,<? XML version = '1. 0'?>).XmldeclarationThe node must be the first node in the document. It cannot have sublevels. It isDocumentThe child level of the node. It can have attributes that provide version and encoding information.